Caffeine 101: Health Benefits, Risks, and Sources

You’re probably most familiar with caffeine from the java jolt you get from your coffee. It’s best described as a bitter substance that’s present in more than 60 plants. (1) But that’s just the official definition. For so many people, caffeine is what wakes them up and gets them going in the morning. Indeed, it’s a psychoactive stimulant that acts on your central nervous system to drive your energy up.

After you consume caffeine, it’s absorbed into your bloodstream, where levels usually peak in 30 to 60 minutes (though the peak can happen in as little as 15 minutes or as long as 120 minutes, depending on the individual). Later, the liver takes over in eliminating caffeine. (2)

While you may pour yourself endless cups of coffee to survive the morning, the Mayo Clinic notes that drinking 400 milligrams (mg) of caffeine a day is safe for healthy adults. (3) That’s equivalent to about four cups of coffee per day — but that all depends on where your coffee comes from. For instance:

• Standard brewed 8-ounce (oz) cup of coffee: 95 mg caffeine (4)
• Standard instant 8-oz cup of coffee: 62 mg caffeine (5)
• Starbucks medium roast (house coffee), 8 oz (short): 155 mg caffeine (6)
• Dunkin’ house coffee roast, 10 oz (small): 180 mg caffeine (146 mg caffeine per 8 oz)  (7)
• Coffee brewed from Keurig, 8-oz cup: between 75 and 150 mg caffeine, depending in part on roasting strength (8)

As you can see, to stay within the safe limit, you should investigate just how much caffeine your specific brew contains. And, if you’re looking to cut down on caffeine, the first step is to reduce your coffee intake, as it’s the most widely consumed source of caffeine, research shows. (9)

Though the chatter is always on coffee, caffeine is found in many other sources, including:

Tea While most herbal teas (like chamomile) are caffeine-free, others contain varying amounts. (10) For instance, green contains about 28 mg per cup, while black racks up more, with about 47 mg per cup. (11)

Decaf Decaf coffees and teas will have minimal amounts of caffeine, about 2 mg. (11)

Chocolate Cocoa naturally contains caffeine. One oz of dark chocolate (70 to 85 percent cacao solids) offers 22.7 mg. (12)

Chocolate Ice Cream This treat also has minimal amounts of caffeine, about 4 mg per 1-cup serving. (13)

Energy Drinks An 8.4-oz can of Red Bull contains 80 mg, while a 16-oz can of Monster contains 160 mg. (14,15)

Cola One 16-oz can has 44 mg. (16)

Caffeinated Water In this instance, caffeine is added to the mix. One brand, Hint Energy Water (citrus flavor), contains 60 mg of caffeine per 16-oz bottle. (17)

Migraine Medication Some over-the-counter migraine drugs contain a combo of pain relievers acetaminophen, aspirin, and caffeine (65 mg per tablet). (18) That said, too much caffeine can actually cause headaches, so watch the amount you consume from other sources.

People often talk about drinking coffee as being a guilty pleasure or a bad habit, namely because of the caffeine. But it doesn’t just perk you up, it also can be a major perk for your health. The breadth of the research is on how coffee affects health, rather than caffeine alone. While it’s true that coffee does contain other beneficial compounds (like chlorogenic acid and antioxidants), it’s also the most widely consumed source of caffeine.

In fact, according to a 2022 report that surveyed almost 27,000 active duty U.S. military personnel, coffee accounted for 68 percent of their caffeine intake, with the rest coming from sodas, teas, and energy drinks. (19)

As long as you’re drinking your coffee black or with a hit of milk (rather than sugary syrups), it’s also a healthy way to get caffeine, according to the U.S. Department of Agriculture’s MyPlate guidelines.

If you want to understand just how your caffeine habit may be shaping your health, you’ve got to consider the research. Here’s a look into just what it may do, based on observational research. Just keep in mind that while these studies suggest a link between drinking coffee and the health benefit, this does not indicate a definite cause-and-effect relationship:

Boost Brain Health When people consumed 200 mg of caffeine after studying images, their memories were enhanced for up to 24 hours later, giving credence to the idea that caffeine can shore up long-term memory, according to a study from 2014. (20) But a 2021 review of recent studies suggested that more research was needed.

Safeguard Your Heart In a study that looked at 185,855 people ages 45 to 75 — including African-Americans, Native Hawaiians, Japanese-Americans, Latinos, and whites — who sipped two to three cups of coffee a day saw their risk of death due to conditions like heart disease and stroke drop by 18 percent compared with non-java drinkers. (21)

Help You in the Gym When caffeine breaks down, it turns into a few compounds that affect blood flow, fat burning, and oxygen capacity, notes the American Council on Exercise (ACE). (22) You may find that drinking a small cup before going to the gym (especially in the morning) can make you feel more energetic and ready to tackle the exercise challenge. In fact, research shows that a small, 6- to 8-oz cup of a caffeinated beverage may be beneficial.

Protect Against Cancer A review published in 2017 looked at 201 meta-analyses and found that drinking coffee was associated with an 18 percent lower risk of cancer. The authors recommend sticking to three to four cups of coffee a day. Specifically, they found that coffee can decrease the odds of prostate cancer, endometrial cancer, melanoma, nonmelanoma skin cancer, and liver cancer. Why? Coffee is rich in disease-fighting and anti-inflammatory antioxidants, and caffeine also has antioxidant properties. (23)

Prevent Diabetes There have been a large number of studies over the past few decades about whether drinking coffee can help prevent or manage type 2 diabetes. In a 2021 meta-analysis review of the relevant research, the report’s authors did find a “robust” association between coffee consumption and a reduced risk of type 2 diabetes. Specifically, they noted that higher consumption seemed to align with lower diabetes risk; and that long-term coffee consumption helped maintain proper liver function, which improved metabolic control and could correlate to a reduced diabetes risk. But the authors did caution that, ultimately, formal proof of a direct cause-and-effect relationship between drinking coffee and preventing diabetes was lacking. (24)

Delay Dementia While research isn’t conclusive that coffee or caffeine may prevent Alzheimer’s, it may help prevent those suffering from mild cognitive impairment from progressing to dementia, according to some research. One study from Australia tracked 227 adults for more than 10 years, using brain imaging and other tests at regular intervals to monitor cognitive response. The authors reported that higher coffee consumption correlated to slower cognitive decline. (25)

Stave Off Depression In one study, over 50,000 women who didn’t have depressive symptoms were followed for 10 years. Those who drank two to three cups of coffee a day had a 15 percent lower likelihood of suffering from depression compared with those who had less than a cup per week. The stimulant effect of caffeine may boost your sense of well-being and energy, the authors note. It may also play a role in releasing happy chemicals, like dopamine and serotonin.

It was only recently that the World Health Organization took coffee off of its list of potentially carcinogenic foods, Harvard Health reports. (27) That’s certainly good news.

But remember that moderation is key when it comes to caffeine. Certainly, if you’re drinking too much, short-term side effects can include migraines, insomnia, nervousness, irritability, restlessness, frequent urination, stomach upset, fast heartbeat, and muscle tremors, according to the Mayo Clinic. And, as they point out, everyone reacts to it differently. It’s important to learn how your body handles caffeine so that you can hit a sweet spot where it perks you up without causing problems. (3)

If you want to sleep well at night, know your limit with how late you should be drinking it. It generally takes four to six hours for your body to eliminate half of the caffeine you drank. (28) The risk is drinking it too late where it interferes with your sleep, then having to compensate the next day with more caffeine — it can be a difficult cycle to get out of. The thing is, caffeine can sap your sleep even if you drink it six hours before bed, research has shown. (29)

Another concern: If you’re pregnant. While the thought used to be that caffeine was off limits for pregnant women, it’s now recommended that they keep their caffeine intake to a certain limit to help avoid complications like preterm birth or low birth weight. The American College of Obstetricians and Gynecologists recommends less than 200 mg per day. (30) If you’re pregnant, the best course of action for you and your baby is to chat with your physician about how much (if any) caffeine is best to include in your diet.

And finally, if you have type 2 diabetes, that’s another time to check your caffeine intake. While it’s associated with a decreased risk for developing diabetes, it can be a different story for people who already have the disease. Caffeine may impact insulin and increase or decrease blood sugar levels. (31) It’s always a good idea to talk to your doctor to see what’s best for you given your individual health concerns.